Arctic Apple
The Arctic Apple is a genetically-modified apple developed by Okanagan Specialty Fruits to prevent browning. While Arctic Apples are not yet available in stores, two varieties have been successfully produced: Golden Delicious and Granny Smith, with Gala and Fuji varieties on the way. The anti-browning property of these apples is intended to increase crop yields by reducing losses due to browning and increase the quality of the crop itself. Arctic Apples are especially designed for pre-packaged apple slices, as the current anti-browning chemical treatment is expensive and produces an off-flavor. Browning occurs in apples that have been damaged. Ruptured cell membranes release phenolics that react with a Polyphenol Oxidase (PPO), producing a quinone polymer that appears grossly as surface browning. PPO is not an essential enzyme for apple. In fact, there is little evidence to support PPO playing a defensive role; PPO levels have not been shown to correlate with better pest resistance or scab formation. Many other plants do not have genes for PPO, suggesting that PPO is not essential for plant survival. Development Arctic Apples do not brown because they contain a DNA sequence that inhibits the transcription of the gene for PPO, so the PPO enzyme is not produced and the browning reaction cannot be catalyzed. This is called gene silencing. This regulatory gene was transformed into very young, actively reproducing apple leaf cells. The PPO-inhibiting protein, known as PGAS, was ligated into a GEN-03 plasmid vector. The PGAS gene codes for a protein that can inhibit all four types of PPO in apple. The vector contained a viral promoter sequence (PCAMV35s) and a nopaline synthesis terminator (T''nos'') so that the PGAS gene would be transcribed at a high frequency.'' The vector also contained the ''nptII ''gene (from ''E. coli) for kanamycin resistance so that the transformants could be screened. This plasmid was inserted into competent ''Agrobacterium tumefaciens ''cells. The ''Agrobacterium ''cells then inserted the plasmid DNA into the apple leaf cells via a type IV secretion system, a special type of pilus. Two types of apple cells received the plasmid, a Golden Delicious variety and a Granny Smith variety. These cells were then grown up over four weeks and analyzed for genetic integrity. The genetic integrity of the transformant apple cells was assessed by their ability to grow in media containing kanamycin, a polymerase chain reaction with primers specific to the ''nptII ''gene (to determine that kanamycin resistance is from ''nptII ''and not another mechanism), and a Southern blot with radioactive RNA probes complimentary to the PGAS gene (to assure that the gene had been incorporated without mutation). The Arctic Apple has demonstrated excellent clonal stability in trees. The PGAS gene was successfully integrated into the apple genome and can be inherited between generations as well as maintained in grafts. The clonal stability of these trees was assessed by genetic sequencing. Controversy Like many genetically-modified organisms, the Arctic Apple has met some controversy. However, Okanagan Specialty Fruits assures that there is a very low chance that Arctic Apple could cross-pollinate with non-GMO apples as the hives used to pollinate Arctic Apple orchards will not be used with any other variety. Additionally, Arctic Apple orchards are sufficiently isolated from other orchards to reduce the chance of contamination. Reference Neal Carter. "Petition for determination of nonregulatory status: Arctic Apple events GD743 and GS784." February 2012. USDA APHIS.